Published: Journal of Chromatographic Science,
ISSN 0021-9665 Volume
38, Number 1, January 2000, pp. 21-26
Supercritical Fluid Extraction and Gas Chromatography or Electroanalysis
of Metal Chelates from Different Sample Matrices
V. Arancibia, R. Segura, J.C. Leiva, R. Contreras, and M.
Valderrama
P. Universidad Católica
de Chile, Facultad de Química, Departamento de Química Inorgánica,
Casilla 306, Correo 22, Santiago, Chile
The supercritical
fluid extraction of Pb(DDC)2 and MoO2(acac)2 complexes is performed. The previously
formed complexes are used in order to simplify the extraction process. In the
extraction cell, 9.0 mg of Pb(DDC)2 or 30.0 mg of MoO2(acac)2 is added. With these
two complexes, a study of static and dynamic extraction as a function of pressure
(1000–2500 psi), temperature (40–160°C), and presence of modifier
(methanol) is performed. Under the best conditions, 5.6 mg of Pb(DDC)2 (2.3 mg
of Pb2+) is recovered. The parameters are 2500 psi of pressure, 160°C of temperature,
0.5 mL methanol (placed in a 10-mL extraction cell), 60.0 min of static extraction,
and 2.0 min of dynamic extraction. It is necessary to add 3.0 mL of methanol to
enhance efficiency on the MoO2(acac)2 complex recovery. Quantitative extractions
of MoO2(acac)2 (9.0 mg of MoVI) are obtained when the experiments are carried
out under 1000–2500 psi of pressure, 140°C, and times no longer than
10.0 min. Then, the study is carried out forming the in situ complexes. For this
purpose, metallic ion and ligand are added. Under these conditions, the Pb2+ recovery
decreases from 2.3 to 1.9 mg, and the MoVI recovery decreases from 9.0 to 1.0
mg. When 1.9 mg of Pb2+ and 1.0 mg of MoVI or less is placed in the extraction
cell, the recoveries are always 100%. The Pb2+ extracts are directly accomplished
using gas chromatography–flame ionization detection (GC–FID), and the
MoVI extracts are analyzed using GC–FID and catalytic adsorption voltammetry.
The quantitation of pure extracts is carried out by constructing calibration curves
with complex solutions and sample solutions using the standard addition method.
This method is applied by determination of Pb2+ in sodium alginate extracted from
algae and blood, urine, and human milk from patients with diagnosed plumbunemy.
MoVI is determined in irrigation water and pasture of animal intake.
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